Xiphophorus fishes are actively being used in fields of study including evolution, sex determination, endocrinology, ethology/behavioral ecology, toxicology, parasitology, immunology, and in cancer research. The number of researchers employing these fishes has steadily risen over the last few decades, as have the associated scientific publications. Studies using Xiphophorus are often hindered by the lack of a robust gene map with markers that can be universally utilized by diverse research groups. Researchers are also hindered by a lack of genomic tools, characterized cell lines, and cell culture methodologies. This grant proposal is focused on enhancing the scientific capabilities of the Xiphophorus animal models. The specific aims are: 1) to saturate the Xiphophorus gene map with 2 cM average coverage and develop sequence-tagged, hyper-polymorphic markers that could be utilized in most intrageneric crosses. Special emphasis will be placed on comparative gene mapping approaches; 2) to establish standardized protocols and cell lines from Xiphophorus fish, and to construct, maintain and partially characterize a murine/Xiphophorus radiation somatic cell hybrid panel. The saturation of the gene map, which continues the expansion efforts of the Xiphophorus linkage map, will aid in assigning 24 multipoint linkage groups for the 24 sets of acrocentric chromosomes and delineate the size of the Xiphophorus genome. The development of microsatellite markers will enable all researchers to perform mapping analyses that can be directly compared to results obtained from other research groups. The establishment of cell lines from a known genetic origin with a small amount of chromosomal aberration will also be performed. These cell lines will be characterized for growth and adhesion properties, and made available to the scientific community. Somatic cell hybrids will also be constructed, between Xiphophorus and murine cells. These new lines will be characterized for retention of fish genetic material and mapping panels will be constructed and be made available to the research community. In sum, these experiments will cumulatively provide scientists with data, materials and techniques necessary to further advance research with these fishes.